Telephone system



Feb. 23 1926.

- L. POLINKOWSKY TELEPHONE SYSTEM Fil d a; 15 1924 2 Sheets-Sheet 1 y MM Feb. 23 1926.

L. POLI NKOWSKY TELEPHONE SYSTEM Filed May 15, 1924 2 Sheets-Sheet 2 NMEN EN \NN QNN 22:2 obi v o 000 000000 OO O Mme/72W E. L 4'00 Pa/M/mwJ/gPatented Feb.

unirs stares PATENT OFFlCE.

LIPA POLINKOWSKY, OF ANT'WERP, BELGIUM, ASSIGNOR. TO WESTERN ELECTRICCOMPANY, INCORPORATED, OF NEW YORK, 12'. Y., A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

Application filed May 15,

T aZZ whom it may concern:

Be it known that I, LllA PoLrNKowsKY,

a citizen of Russia, residing at 14 Rue du Bastian, in the city ofAntwerp, Belgium, have invented certain new and useful Improveinents inTelephone Systems, of which the following is a full, clear, concise, andexact description.

This invention relates to telephone ex change systems in whichconnections are established by machine switching equip ment, andparticularly to systems of this character which are provided for dealingwith traffic of small exchanges.

iin object of the invention is to improve the eiiiciency and simplifythe method of operation of small local telephone exchanges.

In accordance with one feature of the invention, the connecting or linkcircuits used in the establishment of the connections terminate in aplurality of selecting units having access to different groups of lines,and it so arranged that the selection of a particular unit for thefurther extension of a call is effected by means operating under thecontrol of the calling party.

In the preferred arrangement, the lin i5 terminate in a plurality offinal selector switches and the operating magnet of the final selectorswitch having access to the group of lines in which the called line islocated, is chosen by a group of relays selectirely operated inaccordance with the value of the first digit of the called subscribersline designation.

In accordance with another feature of the invention, the selection of aparticular unit and the operation of the selected unit may beaccomplished in response to the setting of an auxiliary or registerswitch operating under the control of the calling party, The setting ofthe brushes of this register switch may determine which relays of thegroup of relays shall be operated to connect up the operating magnet ofa particular selecting unit. 7

According to a further feature, on the release of the connection variousselecting units of a link are tested to determine whether they are innormal position and, if not, they are restored to normal posi tionbefore the link is freed. An arrange ment is provided to insulate thebrushes of the switch if release occurs before the con- 1924; Serial No.713,428

nection is established, so as to avoid interference with other calls. 7

.These and other features of the invention will be fully understood fromthe following description taken in connection with the drawings, inwhich one cord circuit in accordance with this invention is shown.diagrammatically.

In the drawings, a subscribers circuit and a link circuit arranged inaccordance with this invention are diagrammatically illustrated. Fig. 1shows the line ofa calling subscriber, a line finder switch, and apartof a link or connecting circuit. Fig. 2 shows the remainder of thelink or con necting circuit withits associated register switch, and alsotwo of a number of final selector switches which may be adapted forcompleting a connection with a called subscribers line. I

The calling line 101 is provided with the usual lineand cut-off relayswhile the link circuit consists of a line finder switch 102 for makingconnection with the calling subscribers line and a plurality of finalselector switches in which the link circuit terminates, two of which,designated 20 i and 205. are shown. Each final selector switch isirovided with two sets of brushes such as 206 and 207 for switch 204,and 209 and 210 for switch 205, either of which set in the selectedswitch may be connected to the link circuit, depending upon theenergized or deenergized condition of a connecting relay 212.

In the particular arrangement shown in the drawings, each link circuitterminates in seven final selector switches and each final selectorswitch has associated therewith a stepping magnet 218, 2-19, 220, 221,222, 223 or 224: which is enabled to step the brushes of a finalselector switch over the. contacts in the banks thereof. Preferably,each final selector switch has fifty sets of contacts arranged in acomplete circle, the final selector switches having a simple selectingmovement in one direction only.

In order to control theselection of a particular final selector switch,a register switch 217 consisting of the brushes 213, 214, 215 and 216which are stepped over the contacts in the bank by means of the steppingmagnet 225, is provided. The brushes when in normal positions arearranged to rest on the first contacts of their respective banks, asshown in the drawing, but these contacts will be hereinafter consideredas normal contacts and the successive contacts engaged by the brushesafter said brushes have left their normal positions will be known as thefirst, second, third, etc., contacts. The setting of the brush 216 ofthe register switch for the first or hundreds digit, determines whichrelay or relays of the group of relays 226 to 229 is or are energized toconnect up the particular stepping magnet 219 to After the relay orrelay-s energized have locked up, the

, register switch brushes are returned to normal position to render theregister switch available for the next or tens digit.

The group of contacts engaged by the brush 214 of the register switchdetermines the particular group of tens contacts,one of which will beselected for the units digit. The first and second contacts engaged bythe brush 214 are connected together and to the first contact engagedbya test brush 208 of the selected final selector switch (assuming thatswitch 204 is selected), the third and fourth contacts are likewiseconnected together and to the eleventh contact engaged by the testbrush, and in like manner, the fifth and sixth, the seventh and eighthand the ninth and tenth contacts are connected together and to everytenth contact thereafter, such as the 21st, 31st, and 41st contacts,respectively. In this way the setting of the brush 214 places aselectable potential on the first, the 11th, the 21st, the 31st or the41st contact engaged by the brush 208, these contacts being :the firstcontacts of the group of tens among which the final selector switchesmay select the desired line.

It is arranged that immediately the brush 214 has operated for the tensdigit, the stepping magnet of the final selector switch is operated tostep the brushes of the final selector switch until the brush 208engages the contact connected up by the brush 214. Immediately thisselecting operation has been accomplished, the brushes of the registerswitch are restored to normal so that they may beagain moved for theimpulses representing the units digit and the brush 213 connects aparticular contact engaged by the brush 208. When the brushes of thefinal "selector switch are moved and the brush 208 comes in contact withthe contact connected by the brush 213, the brushes of the finalselector switch are brought to rest in engagement with contacts of thedesired line. The selection of a particular set of brushes of theselecting unit is determined by the setting of the brush 215 of theregister switch in accordance with the tens digit. If'this digit is odd,the relay 212 is operated and the upper set of brushes 206 is used,while if this digit is even, the relay remains deenergized and the lowerset of brushes 20? extend the connection.

The sequence switch disclosed in the Reynolds and Baldwin Patent No.1,127,808, of February 9, 1915, the contacts of which are shown in thedrawings and controlled by the power magnet 103 are each closed in thepositions indicated by the small numerals located at theparticularcontacts.

The system illustrated has a total ca pacity of 700 lines. If onlysubstations are connected, the relays226 to 229 and all the steppingmagnets, excepting the stepping magnet 218 associated with the firstselecting unit may be omitted. The capacity of the exchange may beadapted to the number of subscribers lines connected by omitting one ormore of the relays 226 to 229 and stepping magnets 219 to 224.

The selecting unit may be readily adapted for extending a connection toan idle line of a group of lines, or a private branch exchange byproviding a relay 105, the relation of which is hereinafter moreparticularly described. Further, as the groups of lines may be small innumber, the group hunting may be confined to a particular final selectorswitch 204 and may be carried out in only certain hundreds and for thispurpose the relay 105 which controls the group hunting is controlled bythe group of relays 226 to 229 connecting a stepping magnet associatedwith a final selector switch.

This invention will be best understood by tracing the establishment of acall from one subscriber to another.

Establishment of connection.

Vfhen a calling subscriber at the subscribers station 101 desiresaconnection with another subscribers station, the removal of thereceiver from the hook causes thecalling subscribers line relay 106-toop crate from battery through the winding of relay 106, inner leftcontact of cut-01f relay 107, ring side of the calling line, through thesubscribers substation apparatus, baclr' over the tip side of thecalling line,contact and outer left armature of relay 10?, to ground.The line relay 106 connects the left hand winding of the cut-off relay107 to the test terminal of the calling line which test terminal istherefore engaged by the test brush (Z of the line finder 102. Theconnection of the winding of the cut-off reto this test terminal servesto place a selectable potential upon this terminal, therebymarking theline 101 as the calling line.

Operation of Zinc finder.

Upon the energization of linerelay 106 a circuit is also closed for thestarting relay Bil 108 of the line finder switches which have access tothe calling line. This circuit may be traced from battery, through thewinding of relay 108, contact of relay 109, to ground at the leftcontact of line relay 106. The relay 108, upon energizing closes anumber of circuits, one of which for the particular line tinderillustrated in the drawing, may be traced from battery, through the winding of stepping magnet 110, the armature and contact thereof, outer leftarmature and contact of relay 108, lower left contact of earn 111 of theassociated sequence switch, conductor 112, back contact of relay 113 toground at the armature of relay 11 1. The

steppingaagnet 110 of the line finder switch 102 thereupon operates torotate the brushes of the switch over the terminals in its bank and thestepping magnets of other switches which have access to the group oflines in which the calling line is located are also energized in similarcircuits closed by relay 10S. l /hen the calling line 101 is reached thecut-off relay 107 is energized in a circuit which may be traced frombattery, through the left winding of relay 107, contact and rightarmature of relay 100, test terminal engaged by brush (Z of line finderswitch 102, right contact of cam 115, conductor 110, righthand lowresistance winding of test relay 11d, and through the left hand windingof this relay in series, contact of relay 108, upper left contact of cam117 conductor 118 to ground through the normal contact of relay 119.

' circuit and opens at its back contact the uit herein before traced forthe stepping magnet 110 of the line finder switch 102, thereby causingthis stepping magnet to deenergize and to bring the brushes to rest uponthe terminals of the calling line. The relay 11 1-, upon operating,closes a circuit for the lower winding of relay 119, from battery, lowerwinding of relay 119, upper contact of earn 120, conductor 128 to groundat armature of relay 114. The relay 119 thereupon operates and opens atits normal contact the circuit of the high resistance left hand windingof test relay 11 1, but the circuit of the right hand winding of testrelay 111 is maintained closed from ground, through the inner bottomarn'iature of relay 119, cam 121 and its upper right contact, right handhiding of relay 114:, cam 115 and its right contact, conductor 122,brush d of the line finder switch, right armature and contact of relay106, through the lef hand winding of relay 10?- to battery. The innerbottom armature of relay 119 makes with its contact before its normalcontact breaks and the test relay 11st is so wound that it will bemaintained operated over its right hand winding in cir uit with thecutoff relay 107, but the test relay 11 1 will deenergize if there aretwo test relays connected in parallel over The test relay 11 1 energizesin v the same cut-off relay. This operation prevents a plurality offinder switches from simultaneously testing a calling line. If thisshould happen the test relays of all'the switches will becomedeenergized and the circuit of the stepping magnet willbe again closed,so as to step the brushes of these switches away from the calling line,which will be selected by a switch, the brushes of which subsequentlyengage the calling line terminals.

The connection of the low resistance right hand winding of test relay114C to the brush (5 of the line finder switch holds the calling linebusy so no other test relay canbecome energized in parallel therewith.Upon the operation of relay 119 the calling line 101 is extended throughthe two top armatures of this relay to the steppin relay 123. The outerbottom armature or relay 119 closes an operating circuit for thecontrolling magnet 103 of the sequence switch, which may be traced frombattery, through the winding of magnet 1053, cam 1241, cam 125 and itslower left contact to ground at outer bottom armature of relay 119. Themagnet 103 thereupon operates to cause the sequence switch to be drivenout of position 1 and to be moved under the control of master cam 12%into position 2.

The cut-off relay 107 has been operated when the brush cl of line finderswitch 102 engages the test terminal of the calling line and opens atits left inner armature the circuit ofthe line relay 106, so that linerelay 100 is di connected from the calling line and deenergizes, theline relay 106 on opening the contact at its left armature causes thestarting relay 108 to deenergize and this relay by deenergizing opensthe circuit of the stepping magnet of the line finder switchespreviously set in motion so that these switches are brought to rest.

The stepping relay 123 is new under con trolof the dial switch of thesubstation 101. The relay 123 energizes as previously de scribed, inseries with the calling line and closes at its contact and leftari'nature a circuit for the slow-to-release relay 126. The

relay 126 upon operating closes at its con 1 tact before the sequenceswitch has reached positlon 2, and thereby maintains a circuit closedfrom the test brush (Z of the line finder switch, conductor 122, contactof relay 126, left contact of cam 115, conductor 116, right hand lowresistance winding of test relay 11 1, conductor 127, upper rightcontactof cam 121, inner bottom armature of relay 119 to ground therebymaintaining the calling line busy. u

Before the sequence switch has reached position 2, the lower leftcontact of cam 120 was closed in position 1% whereupon a circuit isclosed for the left hand winding of relay 113 from battery, through itswinding,

lower left contact of cam 1.20, conductor 128 to ground at armatureoltrelay 114;. Simultaneously circuit is closed for the right hand windingof relay 113, which may be traced from battery, lower rightcontact ofcam 129, conductor 1&9, cam 130 and its upper contact (closed inposition 1%) brush 213 in normal position, of the register switch 217controlled by the register stepping magnet 225,conductor 131, right'hand winding of relay 113 to ground. The relay 113 upon operatingcloses a locking circuit for itseli which may betraced from-battery,left hand winding of relay 113, lower right and left contacts of cam132, inner left armature and contact of relay 113, lower right and upperright contacts of cam 133, brush 216 oi the register switch in thenormal position, conductor 13%, to ground tln'ouglrlow resistancewinding in the dial tone relay 135. The test relay 111 1 is maintainedenergized in position 2 of the sequence switch from a circuit which maybe traced from battery, through both windings of relay 10?, contact andright armature of relay 107, brush d of the line finder switch 102,conductor 122, armature and contact of relay 126, left contact of cam1'15, conductor 116, right hand winding of relay 114, conductor 12?,upper right contact of cam 121, inner bottom armature and contact'ofrelay 119 to ground.

The dialing tone is now transmitted to the calling line throughconductor 13G, lower left contact or" cam 137, cam 138 and lower leftcontact, through the condenser 177, outer top armature and contact ofrelay 119, brush a of the line finder switch, over the tip side of theline 101, through the subscribers loop to the ring side of the line,brush Z), contact and inner top arma ture of relay 119 to batterythrough the 'winding or relay 123. The calling subscriber 101 uponhearing the dialing tone knows that he may commence dialing the dlgltsrepresentmg the designation of the desired line.

Transmission of hundreds digit.

The transmission of impulses for the first, that is the hundreds digitof the calling line causes the stepping relay to be deenergized a numberof times in accordance with the valueo'f the digit dialed, and thisrelay upon deenergizing closes a circuit for the stepping magnet 225 ofthe register switch, the brushes of which are designated 213, 2 215 and216. The circuit for stepping magnet 225 may be traced from battery,through the winding of magnet 225, through the winding relay 139,contact and right armature of relay 123, back contact and armature ofrelay 1 10, upper right contact of cam 1 11 to ground. The opening ofthe contact at the armature of relay 123 has no effect upon the relay126, as this relay being slow to release maintains its armatureenergized during the transmission of the impulses. The steppingmagnet225, however, responds to the impulses and steps the brushes 213, 21 215and 216 a number of steps corresponding to ceived. The relay 139 whichis located in the circuit of the stepping magnet 225 is arranged to beslow to release and is accordingly operated upon the transmission of thefirst impulses and retains its armature attracted until after the lastimpulse has been transmitted. The relay 139 closes an alternativecircuit for the left hand winding of relay 113, thereby maintaining thisrelay energized after the register switch leaves its normal position.This circuit is necessary as otherwise the relay 113 would deenergizeimmediately the brush 216 of the register switch leaves its normalposition. In peel-on 2 of the sequence switch the left hand winding oftl e relay 113 has connected in parallel therewith a non-inductiveresistance 1422, this circuit being traceable from the'leitt handwinding-of the relay 113, conductor 1 13, upper left contact of cam 141, cam 129, resistance 1 12 to batt-ery. This non-inductive resistanceis pro vided in order to reduce the self-induction of the left handwinding of relay 113 as this is necessary when calls are extend-edautomatically by the dialing 01" the digit 0 of the main exchange.

At the end of the dialing ofthe first digit, the relay 139 deenergizcs,while-the stepping magnet bringsthe brushes 213, 214, 215 and 216 torest'upon a particular set of terminals in the haul: of the switch,corresponding to the value of the first digit dialed and the subsequentselection of the particular connecting circuit to be used in setting upthe cen'.ection d pends upon the terminals engage-d by the brush ot theregister switch. l1 the'brushcs are moved one step, the brush 216 willengage the first contact, which is left dead, no connection being takentherefrom and the relay 113 thereupon deenergizcd as the locking circuitpreviously traced for this relay is now open at the brush 216 oi"- theregister, while the circuit closed by the relay 139 at its contact andarmature for maintaining the relay operated is now opened due to thedeenergization of relay 139. The relay 113 deenergizing, closes at itsback contact and outer left armature a circuit for the sequence switchmagnet 103 which may be traced from battery, through the winding ofmagnet 103, cam 12%, cam

and its upper right contact, back contact and outer left armature ofrelay 113, upper right contact of cam 11-5, cam 141 to ground. Thesequence switch thereupon operates and moves out of position 2 and thenunder the control of this mastercam 12-1, into position 3 where it comesto rest.

It, instead of the digit '1, the digit 2 the number of impulses rehadbeen dialed for the hundreds digit, the brushes of the register switchare stepped into-engagement with the second contact in the bank of theswitch; In this position a circuit is closed for the relay 226, inseries with the winding of the relay 113, so that the relay 113 isprevented fr n deencrgiaing at this stage. This circuit may be tracedfrom battery, left hand winding of relay 113, lower right and lower leftcontacts of cam 132, inner left armature and contact of relay 113, lowerright and upper right contacts of cam 133, brush 216 and the secondcontact in the bank engaged thereby, top winding of relay 226 to ground.The relay upon operating closes a circuit from battery, resistance 1 12,ca1n'129 and its lower left contact, conductor 1%, contact and innerbottom armature of relay 226, top winding of relay 226 to ground, whichcircuit shunts the left hand winding of relay 113. The relay 113thereupon deenergizes and closes a circuit as before explained, for thesequence switch magnet 103, thereby driving the sequence switch intoposition relay 226, upon operating disconnects at its Vbacl: contact andinner top armature the stepping magnet 218 associated with the firstconnecting unit and substitutes therefor the stepping magnet 219associated with the second connecting unit, which stepping magnet isconnected from battery, through the windof magnet 219, back contact andinner top armature of relay 227, front contact and inner top armature ofrelay 226.

If the digit 3 has been dialed for the hundreds digit, the brushes ofthe register switch are moved so as to engage the third contact in theirbanks, and in this positiona circuit is closed for the relay 227 whichmay be traced from battery, hrough left hand wind ing of relay 113,lower right and lower left contacts of cam 132, mner left armature andcontact of relay 113, lower right and,

upper right contacts of cam 133, brush 216 of register switch, the thirdcontact engaged thereby, top winding of relay 22*: to ground. The relay227 renders effective the stepping magnet 220 of the next switch.

I If it is desired to extend the capacity of the exchange beyond 100lines, thereby necessitating the provision of more than four groups ofconnecting units, the relays 228 and 229 will be provided and theserelays would be operated in positions 5, 6 and 7 of the brush 216 of theregister switch to connect up one of the stepping magnets 222, and 224,this operation being similar to that described for the selection of thestepping magnets 218 to 221 and it is not bought necessary to describethis selection in detail.

Should it be desired to extend the connection to the operator at theattendant switchboard, the ea-lhng'subscriber will dial the The minalsin the bank of the switch. As the a.

sequence switch is now in position 2, a circuit is closed formaintaining the relay 113 operated from battery, through the winding 7of relay 113, lower right and 'lower left contacts of canii 132, leftinner armature and contact of relay 113, lower right and upperrightcontacts of cam 133, brush 216 ofthe register switch in position 10,brush 001' the line under switch 102 through the lamp 14'? at theattendant switchboard to ground. The relay 113 remains operated and thesequence switch of the connecting unit remainsin position 2 until thelocal connection is released in a manner to behereinafter described. Y 7

After the dialing of the hundreds digit. and the passing of the sequenceswitch from position 2 into position 3, as hereinbefore described in theestablishmentof a local con nection, the test relay 114: is disconnectedas'its circuit is opened'at the upper right contact of cam 121, whenthis contact leaves position 21/ and in place of the relay 114i, therelay 118 is connected in a circuit which may be traced from. battery,through both windof relay 107 and its contact and right armature, brush(Z and the-line finder switch 102, armatufe and contact of relay 126,through the winding of relay 118, lower right contact of cam 121, innerbottom armature and contact of relay 119 to ground. In order to be surethat the relay 119 is maintained operated during the interval betweenthe deenergiz'ation of relay 114i and the en ergization of relay 1 18,the circuit is closed during the passing of the sequence switch throughposition 2 for the relay 119 which may be traced from battery, throughboth windings of relay 119, upper left con; tact of cam 121, innerbottom armature and contact of relay 119 to ground, but when the relay14:8 operates the upperwinding of relay 11 9 is connected directly toground at bottom armature of relay 118, so as to maintain the relay 119operated. The relay 1418 upon operating, prepares a through connectionfrom the calling line to the brushes of a final selector switch 206%,the selection of theparticular set of brushes to be used beinghereinafter described.

l hcn the sequence switch reaches position 3, a circuit is closed forrestoring the register switch back to its n ,rmal position. This iseffected by closing a circuit over the stepping magnet'225 of theregister switch inatically to stepthe brushes from the position inwhichthey were set by the dialing of the hundreds digit until these brushesreach normal position,"when the, circuit is .traced from battery,through the winding of magnet contact and armature of the magnet, upperright contact of cam 111,

back contact and inner right armature of relay 113 to ground at armatureof relay 11 1. lVhen the brushes reach'normal position a circuit isclosed from battery, through resistance 112, cam 129, conductor 1 19,cam 130 and its lower contact-,brush 214.. on the normal contact of theregister switch, con ductor 150, lower right contact of cam 151,conductor 152, both windings of relay 111, upper left contact of cam 1 5to ground. at cam 1 11. The test relay 111 operates imn'iediat-ely thiscircuit is closed and opens the circuit hereinbefore traced for thestepping magnet 225 of the registering switch.

The test relay 1151 upon operating, closes a circuit for the sequenceswitch extending from lattery, through winding of magnet 103, master cam121, cam 125 and its upper right contact, back contact and outer leftarmature of relay 113, lower right contact of cam 120, conductor 128 toground at armature of relay 111. V l The sequence switch .is driven outof position 3 and into position 1 where it comes to rest. In passingfrom position 3 to po sition 1, the relay 1 13 operates in a circuittraced from battery, through left hand winding. of relay 1 13, lowerleft contact of cam 120, conductor 128 to ground at armature of relay11-1. The relay 113 is held operated in a circuit from battery, throughleft hand winning of relay 113, lower right and lower left contacts ofcam 132, inner left armature and contact of relay 113, lower right andupper left contacts of cam 133, brush 215- of the register switch innormal position to ground. A locking circuit is also provided for theright hand winding of relay 113, and this may be traced from groundthrough the right hand winding of relay 113, upper left and upper rightcontacts of cum 138, front contact and outer left armature o-i relay11-3, conduct-or 157,

lower left contact of cam 144:, conductor 119, cam 129 to batterythrough resistance 1 12, but the right hand winding of the relay 113ren'iains short circuited from ground at armature of relay 111, frontcontact of this relay, cam 120 and its lower right contact, conductor15?, and thence to battery through resistance 1 12 over the pathhereinbefore traced.

Transmission of tens digit.

7 The calling subscriber now transmits the impulses representing thesecond, or tens, digit of the called line designation. This digitdetermines the position in the bank of the selected final selectorswitches 20-1, 205, etc, from which the wipers will move for the unitsdigit- A final selector switch by the "setting of the register switchcon-' trolled by the stepping magnet 225. This switch, as previouslydescribed, is restored to normal at the end of the series of impulsesrepresenting the hundreds digit, and is new stepped from normal inresponse to the tens digit. The contacts in the final selector switchover which the test brush 208 (as suming that switch 201 is selected)sweeps, are connected to tile contacts of the register switch 217engaged by the brush 211 in the following manner: The first and secondcontacts of the register are strapped together and connected to terminalNo. 1 in a final selector switch bank (ngaged by brush 208. The thirdand fourth contacts of the register' switchbank are connected togetherand to terminal No. 11 of the final selector switch. The fifth andsixth'contacts are connected in a similar manner to tern'iinal 21. Theseventh and eighth to terminal 31 and the ninth and tenth to terminal11.

It is arranged that immediately the impulses are received for thesettingof the register switch, the brushes of the final selector switch aremoved automatically from rest into engagement with a contact connectedup by the brush 21-1 of the register. Thus, if the register switchreceives one or two impulses. for the second, or tens, di it, thebrushes. of the selected final selector switch are stepped one step soas to bring the brush 208 into engagement with the first contact. If thebrush 21.1 is moved into engagement with the third or fourth contact.the brushes of the final selector switch will. be moved into engagementwith the eleventh contact in-the bank and so on;

hen the calling, subscriber dials the tens digit, the relay123isdcenergized a number of times, corresponding to the value of thedigit and the circuit of the stepping magnet 225 of the register switchis closed at each deenergization of the relay in a circuit hereinbef'oretraced for the dialing of the hundreds digit, it being remen'ibered thatthe sequence switch is now in position 4-. The operation of theslow-to-release relay 139 causes a circuit to be closed for the leftwinding of relay 1123, thereby maintaining this relay operated after theregister switch has left its normal position, as otherwise the circuitof this winding would be opened at the normal contact connected by thebrush 215 of the register, this circuit being traceable from batterythrough left winding of relay 113, lower right and lower left contact ofearn 132, inner left armature and contact of relay 113, lower right andupper left contacts of cam 133, brush 215 in normal position to ground.As soon as the reg ister switch has moved from its normal po sition, thetest relay 114 is tie-energized, the circuit from battery through theresistance 142, cam 129 and its lower left contact, earn 130 and itslower right contact, brush 214 on its normal contact, conductor 150, l0\er right contactof cam 151, conductor 152-, both windings of relay 114,upper left contact of cam 145 to ground at cam 141, being opened whenthe brush 214 is moved from normal position.

A circuit is now closed for the stepping magnet of the final selectorswitch associated with the particular connecting unit to be used. Thiscircuit may be traced from battery through the winding of magnet 218(assuming that the connecting unit with which this magnet is associatedhas been selected), the armature and contact associated therewith, backcontact and outer top armature of relay 229, back contact and armatureof relay 2 8, back contact and outer top armature of relay 227, backcontact and inner top armature of relay 220, lower right and upper leftcontacts of cam 153, front contact and inner right armature of relay 113to ground at the armature of relay 114.

This circuit causes the stepping magnet to operate automatically to stepthe brushes of the switch with which it is associated from normal andthese brushes will now more until brush 208 thereof comes into en'-gagement with a contact connected up by the setting of the brush 214 ofthe register switch. The test relay 114 is now connect ed to the brush208 of the final selector switch so that the test relay serves to testthe contacts over which brushes 208 move and to stop the final selectorwhen brush 208 reaches the contacts connected by the brush 214 of theregister. The circuit of the test relay 114 istraceable from brush 208,outer right armature and contact of relay 113, upper left contact of cam151, conductor 152, both windings of relay 114, upper left contact ofcam 145, cam 141 to ground. When the brush 208 of the final selectorswitch reaches contact 1 (assuming the register switch to have beenmoved one or two steps for the tens digit), the circuit of the testrelay is completed as hereinbeforc 'i raced to the brush 208 and thenceover the first contact of the bank engaged thereby, contacts 1 or 2engaged by brush 214 of the register switch, lower right contact of cam130, cam 144 and its upper left contact, conductor 143, left winding ofrelay 113 to battery. The test relay 114 is energized and by attractingits armature opens the circuit of the stepping magnet 218 at itscontact, thus bringing the brushes of the final selector switch to rest.

If the digits 3 and 4 had been dialed for the tensdigit, the brushes ofthe final sclector switch would have been moved another ten steps intoengagement with the eleventh set of contacts in this bank. It my bearranged that the brushes of the linal selector switch are stepped at arate approximately equal to that of the brushes of the register switchso that the operation of the final selector switch is finishedpractically at the same moment that the brushes of the register arebrought to rest.

At the end of the tens series of impulses, the relay 13 deenergizes andif the brush 208 of the final selector switch has not reached theterminal connected up by the brush 214 of the register, the relay 113will maintained operated in odd positions of the switch in series withrelay 212 and in even positions of the switch through relay 1.05.

i un'iing that the brushes of the register have been set to an oddposition, the circuit maintaining the relay 113 may be traced lroinbattery through the left winding of relay 113, lower right and lowerleft contacts of cam 132, inner left armature and contact of relay 113,lower right and upper left contacts of cam 133, odd contact engaged bybrush 215 of the register switch, lower winding of relay 212, conductors154 and 1.55, lower right contact of cam 141 to ground. Relay 212thereupon becomes energized, and closes a locking circuit for itself atits contact and inner bottom armature through its upper low resistancewinding, and this connection serves short ,ircuit for the left windingof relay 113. Relay 113, however, is maintained energized through itsright hand winding until the brushes of the final selector switch havereached the position determined by the set ting of the register switch.The circuit of the right hand winding of relay 113 may be traced fromground through the right hand winding of relay 113, upper left and upperright contacts of cam 138, front contact and outer left armature ofrelay 113, conductor 157, lower left contact of cam 144, cam 129 and itslower right contact to battery through resistance 142; lVhen brush 208of the final selector switch reaches the terminals connected up by theregister switch, the test'rclay 114 is operated in the circuithereinbefore decribed over the test brush 208, conductor 156, outerright armature and contact of relay 113, upper left contact of cam 151,conductor 152, both windings of relay 114, upper left contact of cam145, cam 141 to ground. The relay 114 short circuits the right windingof relay 113 at the front con tact and armature of relay 114 so thatboth windingsof relay 113 are short circuited and the latter relaydeenergizes causing the subsquent' release of relay 114. A circuit isnow closed through the back contacts of relays 113 and 114 for restoringthe register switch to normal position, this circuit being traceablefrom battery through the winding of relay 225, associated armature andcontact, conductor 158, upper right contact of ram 111, back contact andinner right armature of relay 113 to ground at the armature of relay114. The register switch is thereupon restored to normal position andwhen this is reached the test relay 114 is operated in a circuit fromground at cam 141, cam 145 and its upper left contact, both windings ofrelay 114, cam 151 and its lower right contact, brush 214 in its normalposition, lower right contact of cam 130, conductor 149, cam 129 tobattery. The test relay 114 operates and opens at its back contact andarmature the circuit hereinbefore traced for the step ping magnet 225 ofthe register switch so that the brushes of the latter are brought torest in normal position.

The test relay 114 upon operating closes a circuit for the power magnet103 of the sequence switch, this circuit being traceable from battery,magnet 103, master cam 124. cam 125 and its upper right contact, baclrcontact and outer left armature of relay 113, lower right contact of cam120, conductor 128, front contact and arn ature of relay 114 to ground.The sequence switch mores from position 4 into position where it comesto rest. The right winding of relay 113 receives current from battery,cam 129, conductor 1 9, cam 130 and its upper contact, brush 213 of theregister switch in normal position. conductor -31 through the rightwinding of relay 113, while the left winding during the movement of thesequence switch between positions 4 and 5, also receives current frombattcry through the left winding of relay 113, lower left and lowerright contacts of cam 120, outer left armature and back contact of relay113, upper right contact of cam 125, cam- 124 to ground. Relay 113therefore operates quickly.

The apparatus is now in condition for receivingv the units impulses fromthe calling station. These impulses set the register switch and thestepping magnet of the selecte-d final selector switch operates to morethe brushes of the final switch into engage ment with a set of contactsmarked by the register.

Trrmsmissz'oa of unit impulses.

to ground- 123 dceergises a numb-er of times in accordance with thevalue of the digit and a circuit is closed for the steppng magnet 225 ofthe register switch as hereinbefore traced for the dialing of thehundreds digit. The magnet thereupon brushes of operates to step the theregister switch from normal 1 position corresponding to the e of theunits digit. The relay 139 e11- izes in series with the stepping magnetupon the first impulses and maintains its armature attracted until afterthe last units impulse has been transmitted. At its contact andarn'iature the relay 139 maintains the relay 113 energized after theregister switch has left normal position. After the units impulses havebeen transmitted the relay 189 decnergises whereupon the relay alsodeeneigiz'es as the circuits hereinb ore traced through the windings ofthe relay 113 a e now both open. A circuit is thereupon established forthe stepping magne selected ilnal selector switch, this c "curt beingtraceable from battery, through t indin of magnet 218 (assuming magnet-218 to have been selected), back contact and outer top arn'iature ofrelay 229, back contact and top armature of relay 228, back not andouter top armature of relay back contact and inner top armature of relaylower right and upper right contacts of cam back contact and inner rightarmature of relay 113 to ground at iature of relay 114. As soon as thebrush 208 of the final selector switch has been noted into engagen'ientwith a Contact which was been connected by the brush 213 of the gisterswitch in response to the dialing of he units impulse, a circuit isclosed for the est relay 114 from ground at cam 1 1, cam 145 and itsupper left contact, both windings of relay 114, cam 151 and its upperright contact, brush 208 and contact engaged thereby, brush 213 of theregister, upper contact of cam 130, conductor 149, cam 129 to battery.The test relay 114 thereupon energizes and opens the circuit of thestepping magnet 218 of the final selector switch, so that this steppingmagnet deenergizes and the brushes of the final selector switch arebrought to rest on the contacts of the desired line... The test relayupon ener izing closes a circuit hereinbefore traced for the sequenceswitch 103. Tl e sequence switch thereupon moves from position 5 intoposition 6.

lVhen the units digit is Zero the brushes of the selector switch are notadvanced for this digit, but remain on the set of terminals to whichthey are moved, as determined by the setting of the register switch forthe tens digit. The test relay 114 is now operated in a circuit over thebrush 213 and the tenth contact engaged thereby. This circuit may all betraced from battery, cam 129, conductor 149, can'1 130, and its uppercontact, brush 213 engagedwith contact zero, conductor 150, lower rightcontact of cam 151,,conductor152, both windings of relay 114, upper leftcontact of cam145, earn 141 to ground. The test relay thereuponenergizes and closes the circuit 'of the sequenceswitch 103 which thenmoves out of position 5into position 6 and is driven into the latterposition by. the cnergization of the relay 140. The relay 140 isenergized in a circuit from battery, cam 129, conductor 149, cam-130andits upper contact, brush 213 and the tenth contact engagedthereby, lowerleft and lower right contacts of cam159, conductor 160, right handwinding of relay 140 to ground. The relay 140 energizes and closes acircuit forthe sequence switch from battery, magnet 103, care 124, cain125 and, its lower right contact, conductor 161,.bacl: contact andmiddleleft armature of relay 105, front contact and armature of relay140, lower left and upperright contacts of cam 153, back contact andinner right armature of relay. 113 to ground at the armatureof relay114, as the test relay 114 deenergized as soon as the sequence switchleft position The sequence switch now moves into position 6 and fromthis point the connec tion proceeds in the manner described.

.In position. 6 of the sequence switch test r lay 114 is used fortesting the busy or idle condition of the desired line. The test circuitmay be traced from either of the test brushes (bottom brushes of brushsets 206 and, 207) according to whether or not the relay 212 has beenoperated, as determined by the value of the tens digit, that is, whetherthis digit is odd or even, thence through the operated or normalcontacts at the outer bottom armature of relay 212,

lower left contact of camrl5l, conductor 152. both windings of relay114, upper left contact of cam 145,to ground at cam 141. 1f the calledline is found to; be busy, the test relay114. does not energize and asthe circuitcf this relay is opened at the upper left contact of cam 145,when the sequence switch moves to position 7 as hereinafter described,the test relay remains deenergized when the sequence switch reaches thisposition. The relay 140 is energized in a circuit from ground, righthand winding of relay 140, upper right and upper left contacts of cam13?, conductor 156, brush 208, brush 213 ofthe register switch, uppercontact of cam 130, conductor 149, cam 129 to battery through resistance.142. The relay 140 thereupon. energizes and closes a circuithereinbefore traced for the sequence switch which thereupon moves fromposition 6 into position 7. In this position, if the test relaydeenergizedin position 6 indicating that the called line is busy, a busytone is transmitted to the callingnline from the busy tonetransformerml64 over ZllI'C11lt fronr' ground, through thetransformer164, lower right contact of cam 137, cam 138 and its lower left eontact,through the calling subscribers loop and right hand'windingof relay 123to battery, and the subscriber is tnereforenotified that the called lineis busy.

Ift-he called lineis found to be free, the test relay 114 is energized,over the circuit hcreinbefore traced and through the cut-off elay 107 ofthe called 1ine.- Therelay'114 closes at its frontycontact,acircuit forthe relay 113 from battery, through the: left hand winding of relay 113,lower leftcontact of cam 120, conductor 128 to-ground at armature ofrelay 114;";The relay 113 upon operating closes a circuit fron' groundihrough cam 141, cam-145' and itslower rightscontact, contact and innerleft armature of relay 113, lower left and upper left contacts of cam132,-th.rough the right hand winding of; relay 114, cam 151and its lower.lcftcontact, conductor 230, normal contact at relay 212, (it beingassumed that relay 2 .2 is deenergized) lJOtlJOlUlWUSll (sleeve) ofbrush set 207 thence to-the test contact of the calling line.Thisconnection through thelow resistance right hand winding of-the testrelay 114 n'iaintains the calledlinebusy. Ashereinbefore described, thetest relay 114 is a marginal. relay and should two finaleelectorswitchcs come to rest simultaneously upon the contacts of aline, the test relay would deenergizeas it is unable to maintain itsarmature attracted when connected with the two cut-off relays inparallel. hen the called line is found to be free, the sequence switch103 upon reaching position '7 is rnaintainedenergized over the circuithereinbefore traced. i

. Thesequence switch moves into position Swliere it comes to rest.

Group hunting.

The final selectorswitches 'may be readily adapted for extendingconnections to free lines of a private branclrexchange group or 7groups. For this purpose the group hunting relay 1.05 is connected so asto be energized in response to. the dialing of a part cular even tensdigit. As group hunting may only be desired on certain hundreds groups,the circuit ofthe relay 105 is also arranged to be controlled by therelays 226, y

227, 228 and 229 controlling the selection of aq'mrticular selectingmagnet 21.8 'to .224 as sociated iwith a particular final selectorswitch of the link circuit. .Thus in the partieular arrangement shown inthe drawing, the relay 105 is connected to the second con tact engagedby'brush 215. of the register switch and the circuit of the relay istaken through the outer top aru'lature of-relay 226 to'ground attheouter bottom armature of relay 227. Thus, in this particulararrangement shown in the drawings, group hunting may only take place inthe first hundreds, that is, when both the relays'226- and 227 aredeenergized, and further this group hunting is only effected when thetens digit is 2. It will, of course, be obvious that any otherarrangement may be effected by a suitable connection to the circuit. ofthe relay 105'-with respect to therelays226 to 229, and also withrespect to the contacts engaged by the brush 215 of theregister.

' If'the calling subscriber desires to extend a connection to a group ofprivate branch exchange lines, he will dial thedigit 1 for the hundredsdigit and the digit 2 for the tens digit. After the dialing of the tensdigit, a circuit is closed'for the relays 113 and 105 from ground atouter bottom armature of relay 227, back contact and outertop armatureof relay 226, through winding of relay 105, second contact engaged bybrush 215 of the register'switch, upper left and lower right contacts ofcam 133 (it being assumed that'the sequence switch is in position 4'),contact and inner left armature of relay 113, lower left and lower riglit contacts of cam 132, through the left hand wind ing of relay 113 tobattery. This circuit maintains therelay 113 energized andoperates therelay 105. The relay 105, upon operating, closes its right armature andlocking circuit for itself which may be traced from battery, through theresistance 142, cam 129 and its lower left contact, rightarmature,'contact and'winding of relay 105, conductor 166, outer toparmature and con tact of relay 226, outer bottom armature of relay 227,to ground. A portion of'the above traced circuit through the lowresistance 142 to the winding of the relay 105 acts as a s'hort'circuitfor the left hand winding of the relay 113, so that therelay 113 nowdeeuergizes. The relay 105 also opens at its outer left armature acircuit of thelow resistance left hand winding of the relay 140 toground so that this relay is now made quick act ng; Therelay 105 alsochanges the connections of the contacts and armatures of the relay 140so as to enable this relay to control the operations of a final selectorswitch during group hunting.

In position 6 of the sequence switch, the relay 140 becomes energized ashereinbefore described, over thebrush 208 of the final selector switch,its circuit being traceable over brush 208, upper left and upper rightcontacts of cam 137, through the right hand winding of relay 140 toground, After brushes of the final selector switch have been set .uponthe first contact of the group of the private branch exchange lines, thetest relay 114 tests this first contact from the bottom brush of brushset 207, this circuit being traceable from the bottom brushof set 207,normal contact of relay 212 (assuming 212 isdeenergizcd), conductor 230,lower left contact of cam 15], conductor 152, both windings of relay114, upper left contact of cam .145 to ground at ram 141.. If this firstline of the-private branchexchangegroup is busy, the relay 114 does notoperate, and a circuit is closed from ground over the back contact ofrelay 114, inner right armature and back contact of relay 113, over thesteppi-ngmagnet 225 of the register switch, which circuit may be tracedfrom battery, through the-winding ofmagnet- 225, the contactand-armatureof magnet 225, conductor 158, upper right hand contact (cut for position 6, but not shown)' of'cam 111, conductor 112, back contact and innerright armature of-relay 113 to ground at armature of'relay 114. Thestepping magnet 225 now operates automat cally to step the brushes ofthe register switch one step from the contacts into engagement withwhichthey were set in response to the units digit. The circuit of the relay140 is now opened at the brush 208 ofthc final selector switch as thisbrush is vno longer connected to a contact of the registerswitch by-thebrush 213 of the latte'ri Therelay 140 releases its armature and closesa circuit for the stepping magnet 218 of the selected final selectorswitch which may be traced from battery, through the winding of'thestepping magnet 218, back contact and outertop armature of relayv 229,back contact and top armature of relay 228, back contact and outer toparmature of relay 227, back contact. and inner top armature of relay226, upper left. and upper right contacts ofcam 16?,inner left armatureand contact of relay 105, back contact-and armature of relay 140, lowerleft and upper right contacts of cam 153, back contact and inner rightarmatureof relay 113 to ground at armature of relay 114.

The stepping magnet 218 of the final selector switch moves the brushesof the latter one. step into engagement with the next set of contacts ofthe private branch exchange. In this position the test relay 114 testsagain; If this-second line of the private branch exchange is free, therelay 114 is operated; If, however, it is busy, the relay 114 remainsdeenerglzed andithe operation hereinbefore described is repeated until afree line or the last line of the private branch enchange group isreached.

If all the lines of the private branch exchange group are found busy andthe final selector switch reaches the last terminal of the group, thetest relay 114 becomes energized in a circuit over this last terminal.which is connected to a cam (not shown) cut for positions 12 and 12conductor 11-0. cam 129 to battery. The test relay closes acircuitfordriving the sequence switch out of'position 6 into position 7.

lVhen the sequence switch leaves position ('5 the contact of the camjust mentioned is opened and the test relay 114 and the relay $.13 aredeenergized and the sequence switch comes to rest in position 7, inwhich position a busy tone is transmitted in the manner hereinbeforedescribed in. the calling sul'istation.

of callecl subscriber.

The called line having been tested and found tree,r1ng1ng of the calledsubscriber is accomplished in position 801 the sequence;

switch- In this position the low resistance right hand winding of thetest relay 114 is connected to ground independently of relay 113 throughthe upper right contact of cam 121, inner bottom armature and contact ofrelay 119 to ground, so that the calling line is kept busy in caseselection is advanced to this stage before release takes place. Acircuitis closed for starting the ringing apparatus through the upper leftcontact of cam 109, this circuit beingtraceableirom battery, throughresistance 142, cam 129, conductor 149,- cam 169 and its upper left contact, through the winding of starting re ay 1680f the ringing apparatusto ground, the ringing current is now transmitted to the called linefrom the source of ringing current through the ringing interrupter 104over conductor 170, lower left and upper right contacts of cam 171,contact and inner top armature of relay 148, iiinertop armature and backcontact of relay 212 (assuming 212 to befldeenergized), middle brush ofbrush set 207, thence through the called line and back to the top: brushof set 207, back contact and outer top armature of relay 2'12, outer toparmature and contact of relay 148, lower right contact of cam 138,conductor 1.72,cam 137 and its upper right contactthrough the right handwinding of ringing cut-oft relay 140 to ground.

As the relay 105 is deenergized in position 8 oi? the sequence switch,the lefthand winding of relay 140 of low resistance is short cirouitedand this has the effect "of :nakingthe relay slow acting so'that it notenergized by the normal ringing current fimviug therethrough over thecircuit just traced. lVhen, however, the receiver at the called stationis removed from the hook upon the response otthe calledisubscriber,l'lllS relay is energ1zed, whereby a clrcuit is closed for the sequenceswitch which may circuit is completed through from the callingsubscriber to the called subscriber.

- Release of the connection.

The release of the apparatus is under the control of the callingsubscriben, At the end of the conversation, when the calling subscriberhangs up, the stepping relay 123 deenergizes, whereby the circuit of theslow acting relay 1261is opened, and this relay deenergizes. Relay 126deenergizes and opens the circuit of the cut-off relay 107, and therelay 148, both of which deenergize. The deenergization of the cut-0Hrelay 107 trees the calling line while therelay 148 upon deenergizingopens the holding circuit of the relay 119 at its bottom armature andcontact so that the relay 119 deenergizes. The relay 119 upondeenergizing closes the circuit 'hereinbefore traced for the sequenceswitch from battery, through the winding oi magnet 103, cam 124, cam 125and its upper left contact, contactiand outer bottom armature of relay119 to ground.

The sequence switch moves from position 9 into position '11. When thesequence switch leaves position 9, the test relay 1.14 is. disconnectedat the lower left contact of cam 151 and over the cut-off relay of theallied subscriber,1 whereupon this line is i'reed. A circuit is nowclosed through the winding of stepping magnet 225 of the register switchfrom battery, through the win ding of magnet 225, the contact andarmature oi magnet 225, upper rightcontactof cum 111, back contact andinner right armature of relay 113 to ground.atarmature of relay 114. Thestepping magnet 225 thereupon operates to restore the brushes. of theregister switch to normal and when these brushes reach normal position acircuit is closed from ground at cam 141, conductor 17 3, cam 145, andits upper left contact, both wind ings of relay 114, conductor 152, cam151 and its lower right contact, normal contact engaged by the brush 214of the register,

lower contact of cam 130, conductor-149, to battery at cam 129. The testrelay'l14 operates, opens the circuithereinbefore traced for thestepping magnet 225, and closes a circuit also hereinbefore tracedforthe sequence switch. 1 The sequence switch thereupon moves frompositioirll into position12. l i a W 1 Position 12 of the sequenceswitchis the position in which the stepping magnet 224. (if such a magnet'isprovided, andis 011 normal) is restored to normal position. In thisposition the relays 228 and 229 are energized: in parallel from groundthrough the upper windings ot' relays 228 and 229.

conductors 231 and 232, upon contacts of cam 174, to battery at cam 129.Relays 22 -8 and 229 thereupon operate and a circuit-is ill closed fromthe steppingmagnet 22%!- throughthewinding of magnet. 224, the armatureand contact of magnet 224-, front contact and inner top armature ofrelay229, front. contact and toparmatureof relay. hack contact and outer toparmature of relay 22?, back. contact and iunertop armature of relay 226,lower right and upper right contact of cam 153 (upper right contactbeing cut for position 12 but. not shown). bar; contact and innerright:armature-of relay 113 to ground at arn'iature of relay 114. The steppingmagnet 2 4, thereupon operates torotate the brushes of the final :"clector ,witch of the unit with which it is associated back to normalposition, and when this position isreached, a circuit is clofed for thetest relay 114 from ground at cam H1, conductor wax-am 145 and itsupperleft contact, throughl:=oth windings of relay 1'14, conductor-152, cam151 and its upper right contact, conductor 156, test brush (similar tobrush 208) of one of the seven liuul selector switches (not shown. buthereinbefore mentioned) and which switch is controlled by steppingmagnet 224-, normal contact in associated switch bank, a contact and cam(also not shown) cut for positions 12 and 12 A, conductor 149 to batteryat cam 129; The test relay 1'14, operates in this circuit and closesthecircuit of the sequence switch which thereupon moves from position 12 toposition 13. Y

If. however, a circuit is provided with a stepping magnet such as 22 1,and the brushes controlled by the stepping magnet arein normal positionwhen the release'taltes place, the relay 11l'becomes energizedimmediately the release is initiated over the circuit hereinbeforetraced. The relays228 and 229beco1ne energized in a circuit whichincludes their upper windings in' parallel, through the conductors'231and 232 to bat- .tery at cam 129' as hereinbefore traced. Po"- sition-13is the position in'which the-stepping magnet 223 (if provided and if offnormal) is restored to normal position. In position 13, the relay229only is energized in a circuit from ground; upper winding ofrelay229; conductor 23-1, upper left contact of cam 174:, cam 129 to battery.The relay" 229 operates and closes a circuit. for the stepping magnet223 from. battery through the winding of magnet 223, armature andcontact of magnet 223, front contact and outer top armature of relay229, baclccontact and armature of relay 228 (it being remembered that228-deenergized when sequence switch moved from position- 12), back.contact and outer top armature of relay 227, back contact and inner toparmature of relay 226, lower right and upper right contacts of cam 158,back contact and inner right armature of relay 113-130 ground atarmature of relay 11.4. The stepping. mag net? operates to restore thebrushes associated therewith to normal position when the test brush(similar to. 208), of. the set of brushes (not shown) controlled by thestepping. magnet. 223 is in normal position,.a circuit is closed for thetest relay 11st from ground at cam 141, conductor 1723, cam 1 15 and itsupper left contact, .both windings of test relay 11 1, conduct'or1'52,cam 151' and its upper right contact, conductor 162,.test brush (notshown,,but. similar to 208) controlled by stepping magnet 223, normalcontact in the associated switch=banlthence connected to a cam (also notshowm) cut. for positions 13 and-13%, conductor 1.49 to battery at cam129. The. test relay. energizes and opens a circuit hereinbefore traced.for the stepping magnet 223 so as to bring the brushes associatedtherewith to rest and closes the circuit. for' the sequence switch.which thereupon imov es to position 14.

In position 14 the relay 228'is energized through its upper winding fromground. conductor 232,.upper right contact of cam 17 1-, cam 129 tobattery. Relay 228 upon operating. closes thecircuit of thesteppingmagnet 222. ifv the brushes controlled by this magnet are offnormal, this circuit being traced from battery through the winding of.magnet 222, the associated armature and contact, backcontact and innertop armature of relay. 229,.front contact and top armature of relay228,. back contact and outer top armature of relay. 227, back contactand inner top arn'iature of relay 226, lower right and upper rightcontacts of cam 1'53 (upper right contact cut for position 14, but notshown) back contact and inner right armature ofrelay 113 to ground atback contact and armature of relay 11 1. The stepping magnet 222thereuponoperates to step the brushes associated therewithback to normaland when this. normal position is reached, the test relay 11-1 energizesin a circuit: fronr: ground at cam 1 11, cam 1.15 and its upper leftcontact, through both windings of relay 11. 1, conductor 152, cam 151and its upper'right contact, conductor 156; test brush (not shown, butsimilar-to 208) controlled by stepping magnet 222, normal'contact inassociated switch bank, hence connected to a cam (also not shown) cut:for position 14 and 1 1 conductor 149 to. battery cam 129. The testrelay 114' operates, opens a circuitof the stepping magnet 222, andcloses the circuit of the sequence switch which now moves from positionH to position 15 where it comes to rest.

in: position both relays 226 and 227 are energized through their upperwindings iuparallel conductors 234 and 233. the upper right and 'upperleft contacts of cam p front contactand inner top armature of re 129to-battery. These relays thereupon operate and connect thcsteppingmagnet 221 from battery through the winding of magnet 221, armature andcontact of relay 221, front contacts and inner top armatures of relays227 and 226, lower right and upper right contacts of cam 158 (upperright con-'- tact being cut for position 15, but not shown), backcontact and inner right armature of relay 113to ground at armature ofrelay 114. The stepping magnet 221 ro tates the brushes associatedtherewith if off normal back to normal position when circuit is closedfor the test relay .114 over the test brush similar to 208) of the setof brushes (not shown) associated with the stepping magnet 221, normalcontact engage'd thereby, hence connected to a contact of a cam, (notshown) cut for positions 14% and 15%. The test relay operates, opens thecircuit of the stepping magnet 221 and closes the circuit for thesequence switch.

which moves from position 15 into position 16. In position" 16 only therelay-227 is energized from ground, through the upper winding of relay227, upper left contact of cam 129, to battery.- The relay 227 coirnects upthe stepping magnet 220 and if the brushes associated with this"switch are off normal this magnet is operated to move -these brushesback to normal position and when this position is reachedthe. test relay114 is'energized in a circuit including the test brush (similar to 208)of the set of brushes (not shown-)"associated with the stepping magnet220, normal contact engaged by this brush," hence connected to a cam(not shown) cut for positions 15 and 16 ,4 The testrelay uponoperatii'ig opens the circuit of the-stepping magnet 220 and closes thecircuit of the sequence switch so that the sequence switch moves from.position 16 into position 17.

In position 17 the relay 226 only is energized over a circuit fromground, winding of relay'226, conductor234, upper right contact ofcam129 to battery, and the stepping magnet 219 is energized through" thelay 226. The stepping magnet will operate to 'rotate the brushesassociated therewith if off normal back to normalposition and -when thisposition is reached. the test relayl 114 is energized over the testbrush :21]; associated with this stepping magnet and normal contactengaged thereby, hence connected to a cam (not shown) cut for positions16%; and 17 so that the test relay upon energizing opens the circuit ofthe stepping magnet 219 and closes the circuit of the sequence switchtomove it froin position 17 to'position 18; i

' In this position the relay 226 is de-" energized 'and the steppingmagnet 218 is energizedthrough the normal contacts-at tion and closesthe circuit of the sequence I switch soas to more the sequence switchfrom position 18 into position '1 the normal position.

System including tivo digits,

Tn the system'described and illustrated in the drawing, it has beennecessary to transmitthree digitsin order to obtain the calledsubscriber. If, however, the capacity of the system has not yet beenextended beyond one hundred lines, it may be-readily arranged that onlytwo digits are necessary for establishing the desired connection;

I This is accomplished by causing thc sequence switch to pass positions2 and 3 and to move into position 4 in which the dialing tone is given.For this purpose the I upper] right contact of cam 133is shown connectedto the brush 216 of theregister switch.

"The relays 226 to 229 and'the stepping magnet 219 to 224 are omitted.when, there- 'fore, the sequence switch moves out ofv po-" sition 1, asbefore described, the relay 113 will be energized in ac1rcu1tfrombattery J'through the left'hand winding of relay 113,

lower left contact of cam 120 cut for posi- I tion 11%, conductor 128,front contact and armature of relay 114 to ground. The look- 'ingcircuit of relay 113, however, extending from battery, through itsleft-hand winding, lower right and lower left contacts of cam 132, innerleft armature and contact of facts of cam 133. is open at the latterconact as hereinbefore described, so that the relay 113fldeenergizes andcloses the circuit for the sequence switch from battery through thewinding of magnet 103, cam 124, cam 125 audits upper rightcontact,'bacl; contact and outer left armature of relay: 118, upperright contact of cam 14'5, conductor 173 to ground at cam 141; Thesequence switch -thereupon moves toposition3. In this posiwhich is relay113, lower right and upperright concloses a circuit of the sequenceswitch from battery through the winding oft magnet 1203, cam 12%, cam125 and its upper right contact. back contact and outer let't armatureo't'relay 113, lower rightrcontact ot' "car-1 120, conductor 128 toground at arn'iature of relay 114. The sequence switch thereupon movesto position 4 and in this'position, it

is arranged totransinit the usual dialing tone to the calling subscriberthrougli'the conducto1 136 and the lower right and upper left contactsof cam 171. The starting cir- -cuit of the dialing tone apparatus is nowconnected by way of the upper left contact of cam 133 and brush 215 onits normal contact to ground.

The starting circuittor the dialing tone apparatus may now be tracedfrom battery,

through the left hand winding of relay 113, lower lett contacts of cam132, inner left armature and contact of relay 113, lower right and upperright contacts of cam 133 '(the upper-right contact would in this casebe cut for position it) brush 2160f the register switch in normalposition, conductor 134: to ground through the winding otstart ing relay.135. The calling subscriberupon hearing the dialing tone will nowtransmit the -'digit representing the number of the calledsnbscribcfishne, the first digit being the tens digit and operating inthe manner hc'reinbefore described to'cause the stepping magnet 225 ofthe register switch to set its brushes to 'a predetermined position. Theregister switch is restored tonormalposr-f tion immediately the brusheso t the first unit associated -with the stepping magnet 218 are set tothe first set of contacts of the tens group in which the line of thecalled subscriber is located. The second digit which :is the unit digit,again sets the register to cause the brushes of the unit to be moved tothe cont-acts of the called subscribers line. In this way, the hundredsdigit which in the circuit hereinbetore described selects 'a steppingmagnet associated with-a particu- 'lar unitot' the final selectorswitchis omitted,

the first digittransmitted being the tens \IlHCll. 1n the. mannerherembetore described,

effects the setting of the brushes of the first -unit 4 It the callingsubscriber-dials a designa- 'tion whiclrdoes not exist,--a hundredsdigit awould in this case be -e1ther 8 or 9 and the brush 216 ofth'eregister would be setto cither the eighth or ninth contact. The re-"lay- 113 nowremains operated in, position of thesequenceswitch in acircuit from' battery, through -the left hand winding of relay 118,lower right and lower deft contacts of cam 132, inner left armature andcontact "of relay 113, lower r1ght and upper right contacts'ot cam 133,brush 2160f the register switch. conductor 160, through the righthandwinding of relay 140 to-ground. The

operationof the relay 113 prevents the clo sure of the sequence switchcircuit'while the circuit er the stepping magnet 225 is open at its backcontact and armature of relay H0 The sequence switch is thus preventedfrom moving from position 2 until the ca lling subscriber hangs up hisreceiver to release the connection.

lV hat 1S claimed is:

1, Ina telephone. system, subscribers lines arranged 1D groups, aplurality oit'v separately operable selective switches each havingaccess to a-d1fierentgroup of said lines, a single link circuitterminating 1n all ot*-said "switches, a register individual te -said"link CllGUlt, and means controlledxby said =regsaid switches and foroperating the selected switch to extendisaid link circuitito one-of thesubscribers lines. v

3. In a telephone system, subscribers lines arranged in groups, aplurality of selective switches each having a separate ste'ppiingymagnet tor op'era'ting the same and each having access to a ditl'erentgroup oi said lines, a single link'circuit terminating n all of saidswitches, a register tor extending said link circuittoanjyof saidswitches, and

.mea'ns controlled by said register fol-select- 'ing one of saidswitches EIIKlfOl' operating the stepping magnet to extend saidlinltcircuit to one of said subscribers lines.

In a telephone system, subscribers lines arranged'in groups, aplurality-of selective switches, a separate propelling means tor drivingeach of said switches, each of said switches'having access to a'ditterent group of lines, a single link-circuitterminating in all ofsaid switches, and a registerindividual to said link circuit, responsiveto one'se-' ries of pulses to'select one otsaid switches andresponsive'to other series toconnectthe selected switch *to'one ofsaidsubscribers lines. a I r i '5, In a telephonesystem, subscriberslines arranged in groups, a plurality of selective switches, astepping.magnetytor operating each of said selective switches. asinglelink circuitterminating in all of said switches,

a register individual --to said link circuit, a group of relays forselecting one of said stepping magnets, and means controlled by :saidregister for variably operating "said re lays to cause said magnet tostep one of said selective switches into engagement with one ofsaid'subscrihers lines.

In a telephone system, a plurality of groups of subscrihers lines, alink circuit, a plurality of selective switches in which said linkcircuit terminates, each of said selective switches adapted to extend aconnection to a line of one oi said groups, and means operlU able uponthe release of said connection to test said selective switches in orderto detern'iinewhether they are in normal positions, and StllcllllQZlIlSbeing also operable if said selective switches are found in oft-normalpositions to restore them to. normal positions before said link circuitis released.

In Witness whereof, I hereunto subscribe my name this 29th day of AprilA. 1)., 1924:.

LIPA. POLINKOWSKY.

